or that if they are there you don't know about it until they hit you? (a very bad thing)
Its a very bad thing. The situation changes from country to country as the years go by, but its always still a possibility.
Here a short quote form
The UN,
The draft refers to a C-130 transport aircraft shot down on Dec. 26 with 10 U.N. staffers and four crew members on board and to a second plane, which was carrying four crew members and five passengers, including the son of the pilot of the first flight, when it went down on Jan. 2.
You can also browse
this website and scan the hull losses in the African countries. Makes for amazing, yet sad reading.
PS. Big, clearly visible UN and WFP markings on white aircraft mean nothing to some of these guys.......